Colored light sources are often used in the theater, television, touring productions, and architectural applications. The color is varied in hue, saturation, and intensity to obtain a particular artistic effect. The artistic requirements might be that the color remain static, or that it change over time. Cost, speed of changing colors, the quantity of colors produced, the smoothness of color changing, compact size and weight, and the efficiency of transmitting light through color filters are all factors in the practical usage of a color changing system.
One prior art method of changing the color of a light source is to manually insert a specific color filter in the light's path to obtain a specific artistic result. This method required that the filter be changed if it did not result in the exact color that was desired. Changing a color filter required the procurement of the new color filter and the replacement of the old filter. This use of specific filters makes it impractical to change the color of the light during a performance. The filters most often used in these applications are dyed or coated plastic films called gel. The durability of this material is limited and requires frequent replacement when used with a high powered light source. The general efficiency of light transmission is low. In the creation of certain dark blue and red colors, transmission can be as low as 2%.
Since the introduction of the use of gel as a color filter, inventors have created several methods to remotely change the color of a light source utilizing gel. The Scroller.sup.tm, by Wybron of Colorado Springs, CO, assembles a plurality of different colored gels into a band that is fitted around a pair of scrolls. The scrolls are spaced on opposite sides of the light source's aperture. By rolling the scrolls, any of the colors on them can be accessed. This method and its variations, embodied in products manufactured by a number of companies, is a compact solution to changing color. However, the method has many deficiencies. The mechanism to locate and control the scrolls is costly and complex. Gel deteriorates in a short time when rolled back and forth on a scroll while being subjected to heat from a light source. Furthermore, the number of different colors that can be used at one time is limited to the number of colors that are able to be assembled into a single gel band. The slow speed of color changing, the low transmission efficiency of the filter material, and the need to frequently replace gel filter material are also deficiencies in this prior art method.
U.S. Pat. No. 5,126,886, to the present inventor Richardson, discloses an improved scroll type gel color changer. Yellow, cyan, and magenta scrolls of varying color saturation are located in series in the optic path. The various position locations of the three scrolls result in an unlimited number of colors. Colors can be changed quickly or slowly. The transition from one color to another is smooth. The mechanism of this color changing system has three times the complexity of the single scroll system and therefore suffers in cost and reliability.
Other inventors have created several other methods to change the color of a light source utilizing interference or dichroic type filters. Dichroic filters are efficient in transmitting light and are durable, but they are costly. U.S. Pat. No. 5,073,847, to Bornhorst, issued Dec. 17, 1991, and U.S. Pat. No. 5,186,536, to Bornhorst, et al., issued Feb. 16, 1993, disclose a method of tilting a series of dichroic color filters to create various colors. However, this system is limited in the quantity of colors that it creates, the excessive cost of the color filters, and the fact that the system requires a very complex control mechanism.
U.S. Pat. No. 4,914,556, to the present inventor Richardson, issued Jun. 30, 1992, discloses an assembly of yellow, cyan, and magenta filter wheels, each with varying levels of color saturation. The positioning of the wheels between a light source and an aperture determines saturation and hue of color at the aperture. This module creates an unlimited quantity of colors, however at a relatively high cost. The filters of this module must be many times greater in size than the aperture. This results in a very high cost to aperture size ratio.
Accordingly, it is an object of the present invention to provide a compact and simple, and therefore reliable, light color control mechanism that is inexpensive to produce and maintain.
It is a further object of the present invention to provide a device that, given a white light source, can emit any color chosen by a user. The device can also change from one color to any other color quickly and smoothly.
It is a still further object of the present invention to provide a device that efficiently transmits light.